In general, protection structures for protecting human life and major facilities from external attacks or dangerous materials due to enemy's shelling with shells or missiles are built not only on military sites but also in areas near the military sites. The protection structures are built with thick walls and slabs in the form as a bunker using earth or reinforced concrete and are installed on the ground or underground.
The recent North's shelling onto Yeonpyeong Island vividly shows that not only military sites but even civilian facilities could be exposed to attacks any time under the current situation of inter-Korean confrontation. It points out that underground bunkers or protection structures for protecting human life from such attacks and an efficient operating policy therefor are required.
Moreover, if the currently used reinforced concrete bunkers or protection structures are damaged by an attack, cracks may develop in all directions due to solid properties of sections of materials of the bunkers or the protection structures, and damages are likely to spread to the entire sections. If the thickness of the bunkers or the protection structures is increased to prevent this, a vast amount of material has to be consumed, and the weight of the bunkers and protection structures also increase.
Thus, the needs arises for establishing a protection structure, which localizes a range of collapse in an attack by an enemy to thereby minimize damages of military units or civilians, which is further applicable to major national security facilities and military reservation facilities, and which is economical and is equipped with multiple safeguards.